More particularly, the invention relates to a magneto-optical imaging method comprising:                positioning, close to a target material, a substantially plane face of a magnetic active material suitable for producing a Faraday rotation in a polarized light beam,        generating an exciting magnetic field with angular frequency ω in the target material,        directing a polarized incident light beam, through the active material, toward the target material,        detecting, using photodetector means, a reflected beam corresponding to the reflection on a reflecting surface located between the active material and the target material, and        observing the angle of Faraday rotation in the reflected beam, with respect to the incident beam, which is created in the active material by an interfering magnetic field produced by the target material.        
Such methods, as well as magneto-optical apparatuses implementing such methods, are already known, in particular, by virtue of documents U.S. Pat. No. 4,625,167, U.S. Pat. No. 4,755,752, U.S. Pat. No. 5,053,704 and U.S. Pat. No. 5,446,378.
Such methods and devices are generally used, but not exclusively, to undertake nondestructive testing by eddy current. They combine the use of eddy currents and of the Faraday effect. They make it possible to detect defects, such as cracks at the feet of rivets or corrosion, that are present in a conducting target.
They find applications especially in the aeronautical and nuclear industries.
However, the known methods and devices allow only a qualitative characterization of a defect. The images obtained are binary.
An object of the invention is to provide a magneto-optical imaging method and device allowing quantitative characterization of defects.